Titan's temperature profile is an indicator of the
atmospheric energy transport, by radiation, convection and
conduction. From the surface up to ~250 km altitude,
the temperature profile was measured by the Voyager 1 radio
occultations and infrared spectra. In the troposphere,
heating by the surface and low atmosphere by solar radiation
absorption and cooling by emission to space are the dominant
processes that establish the temperature profile, which
decreases from ~94 K at the surface, to ~70 K at
200 km. Between 200 and 350 km, the atmosphere radiative
absorption and emission balance, and the temperature is
approximately constante. At 250-500 km altitudes,
observations of stellar occultations reveal oscillations
between 170 and 150 K. Atmospheric models predict the
existence of a mesosphere, in the region 350-550 km, with
the temperature decreasing from ethane and other
hydrocarbons' emissions. In this work we analyze emission
lines of methane's \nu4 band (8.1 \mum, 1230
cm-1) with high resolution spectra. The line profiles
of different intensities allow us to determine the vertical
temperature profile for the region 100-600 km, which was not
possible with previously available data. We present the
first infrared observation that can measure independently
the temperatures for the regions 100-200 km, 200-400 km, and
400-600 km. These measurements show the existence of a
mesosphere, with a temperature drop of at least 15 K from
380+50-100 km altitude.

Paulo Penteado is sponsored by the NASA Planetary Astronomy
Program and the Brazilian Government through CAPES.